Curiosity Blog, Sols 4695-4701: Searching for Answers at Monte Grande

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Curiosity Blog, Sols 4695-4701: Searching for Answers at Monte Grande

NASA’s Mars rover Curiosity acquired this image of the “Valle de la Luna” drill hole using its Mast Camera (Mastcam) on Oct. 19, 2025 — Sol 4693, or Martian day 4,693 of the Mars Science Laboratory mission — at 02:04:29 UTC.
NASA/JPL-Caltech/MSSS

Written by William Farrand, Senior Research Scientist, Space Science Institute
Earth planning date: Friday, Oct. 24, 2025
Curiosity has successfully drilled its 44th hole on Mars, which is a major milestone in our investigation of the enigmatic “boxwork unit,” a region of resistant ridges surrounding pits or “hollows” of less-resistant rock. The drilling took place over the past weekend within the “Monte Grande” hollow at the “Valle de la Luna” target. 
Rover planning this week consisted of ensuring that the granular drill tailings from Valle de la Luna were transferred to the SAM (Sample Analysis at Mars) and CheMin (X-ray diffraction) instruments, and analyzing the results. Results from these instruments, which will provide mineralogical and other compositional information, will be especially critical for determining how the boxwork features formed, since chemistry from the APXS and ChemCam instruments and reflectance spectra from ChemCam have revealed subtle, but not striking, differences between the rocks making up the ridges and those making up the hollows. Thus, a compositional explanation for the differences between the two terrain types has yet to be determined.
While these internal studies of the Valle de la Luna samples were going on, remote sensing data were collected by Mastcam of a series of targets, as well as atmospheric remote sensing. Among the Mastcam studies being conducted is a photometry study, a kind of study usually only carried out during an extended stationary period, such as the current drill campaign. Photometry is the study of changes in the apparent reflected brightness of rocks and soils based on the illumination geometry (for example, whether the Sun is low on the horizon or high in the sky). During this photometry campaign, multiple images are collected of the same target regions at different times of day.
In the final plan of the week, as part of the ongoing assessment of the Valle de la Luna sample, material will undergo an evolved gas analysis (EGA) in which the drilled sample is baked in an oven in SAM and volatile molecules including H2O, CO2, and SO2 are released and used to further aid in the characterization of the target materials. Mastcam observations will include further images collected as part of the photometry campaign. Also mosaics of the west wall of the Monte Grande hollow will be collected as well as several atmospheric measurements.
Next week the rover will continue analyzing the drilled sample with more SAM experiments, and also analyze the tailings. The team is also starting to search for a suitable drilling location on a ridge as the next drilling site, in order to compare with the results from the Monte Grande hollow.

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NASA’s Mars rover Curiosity at the base of Mount Sharp
NASA/JPL-Caltech/MSSS

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Last Updated

Nov 13, 2025

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